Distributed file transfer with high performance

ABSTRACT

A method for distributed file transfers with high performance and reliability includes creating, on a first Trivial File Transfer Protocol (TFTP) server, a global cache, where the global cache is used to store up to a first portion of a data file. The method further includes storing, on the first TFTP server, in the global cache, one or more continuous data blocks that have exceeded a defined first request rate threshold, where the one or more continuous data blocks make up a subset of the data blocks of the first portion of the data file. The method further includes predicting, on the first TFTP server, a next data block in the data file to be stored in the global cache and in response to predicting the next data block, storing, on the first TFTP server, the next data block in the global cache.

BACKGROUND

The present invention relates generally to the field of file transfers,and more particularly to file transfers in large scale environments.

Trivial File Transfer Protocol (TFTP) is a simple, lockstep, filetransfer protocol that allows a client to request a file from, ortransmit a file onto, a remote host. TFTP is mainly used during a devicebootstrap process for downloading device OS/firmware and configurationfiles. TFTP is typically used for copying bootstrap and configurationfiles between nodes belonging to the same local area network (LAN).

TFTP is used along with boot protocols such as bootstrap protocol(BOOTP) and dynamic host configuration protocol (DHCP) to initializedevices. When an internet protocol (IP) enabled node boots up, the nodegets an IP address and other device and network related parametersthrough BOOTP or DHCP. As part of these parameters, the client alsoreceives the TFTP server address, bootstrap file and configuration filedetails (file name and directory location). The client then uses theTFTP protocol to download the bootstrap image and configuration filesfrom the TFTP server.

SUMMARY

Embodiments of the present invention disclose a method, computer programproduct, and system for distributed file transfers with high performanceand reliability. The method includes creating, on a first Trivial FileTransfer Protocol (TFTP) server, a global cache, wherein the globalcache is used to store up to a first portion of a data file. The methodfurther includes storing, on the first TFTP server, in the global cache,one or more continuous data blocks that have exceeded a defined firstrequest rate threshold, where the one or more continuous data blocksmake up a subset of the data blocks of the first portion of the datafile. The method further includes predicting, on the first TFTP server,a next data block in the data file to be stored in the global cache andin response to predicting the next data block, storing, on the firstTFTP server, the next data block in the global cache.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating a distributed filetransfer environment, in an embodiment in accordance with the presentinvention.

FIG. 2 is a flowchart depicting operational steps of a global cachesoftware, on a TFTP server cluster within the distributed file transferenvironment of FIG. 1, for inserting a head data block in a globalcache, in an embodiment in accordance with the present invention.

FIGS. 3A and 3B depict a head data block being inserted in a globalcache by a global cache software, within the distributed file transferenvironment of FIG. 1, in an embodiment in accordance with the presentinvention.

FIG. 4 is a flowchart depicting operational steps of a global cachesoftware, on a TFTP server cluster within the distributed file transferenvironment of FIG. 1, for removing a tail end data block from a globalcache, in an embodiment in accordance with the present invention.

FIGS. 5A and 5B depict a tail end data block being removed from a globalcache by a global cache software, within the distributed file transferenvironment of FIG. 1, in an embodiment in accordance with the presentinvention.

FIG. 6 depicts a block diagram of components of the TFTP serverexecuting the global cache software, in an embodiment in accordance withthe present invention.

DETAILED DESCRIPTION

Embodiments in accordance with the present invention recognize a needfor a method for distributed file transfers with high performance andreliability.

In Trivial File Transfer Protocol (TFTP), a transfer is typicallyinitiated by a client issuing a request to read or write a particularfile on a server. Both devices involved in a transfer are consideredsenders and receivers. One device sends data and receivesacknowledgments, and the other device sends acknowledgments and receivesdata. A TFTP request can optionally include a set of negotiated transferparameters proposed by the client the block size. Upon granting therequest, the file is sent in fixed length blocks of 512 bytes by defaultor the number specified in the negotiated block size. Each block oftransferred data, which is usually carried within a single IP packet inorder to avoid IP fragmentation, must be acknowledged by anacknowledgment packet before the next block can be sent. A data packetof less than 512 bytes or the agreed block size option signalstermination of a transfer. In the event that a packet is lost in thenetwork, the intended recipient will timeout and may retransmit the lastpacket (which may be data or an acknowledgment), thus causing the senderof the lost packet to retransmit that lost packet. The sender keeps justone packet on hand for retransmission, because the lock stepacknowledgment guarantees that all older packets have been correctlyreceived.

One type of TFTP transfer is a traditional master-client configurationwhere one or more TFPT clients are assigned to a single TFTP server.When using a traditional master-client configuration in largeenvironments with thousands of nodes, multiple TFTP servers can be usedand can have assigned groups such as 1024 nodes, or clients, per TFTPserver. In this type of configuration, each TFTP server can acceptrequests from the assigned group, however, the configuration does notprovide high availability. When a TFTP server goes down, the entireassigned group is affected. Throughput is also an issue. For example, ina configuration with 1024 nodes per group and a file size of 16gigabytes, the throughput at the TFTP server would be severely degradedand the TFTP server would become a bottleneck.

Another type of TFTP transfer is a traditional type master-clientconfiguration using multiple TFTP servers (i.e., TFTP worker servers,also referred as worker nodes), behind the master, or primary, TFTPserver. This type of configuration can improve the performance of filebuffers and the throughput of reading the file from disk with theadditional TFTP worker servers, however all data must flow thorough themaster TFTP server which can be a bottleneck in a very large environmentregardless of the network speed.

Embodiments of the present invention provide a computer-implementedmethod for distributed file transfers with high performance andreliability. The method includes an TFTP server cluster, wherein eachTFTP server in the TFTP server cluster is fully symmetric of oneanother. For example, there is no distinct relationship between thenodes in the cluster (e.g., there are no primary nodes and workernodes). Every TFTP server in the cluster can receive TFTP requests fromTFTP clients directly. The method also includes the TFTP clientselecting an TFTP server by using a Consistent Hash Algorithm. Forexample, upon executing a boot sequence, a TFTP client can broadcast apreboot execution environment (PXE) request to a Dynamic HostConfiguration Protocol (DHCP) server. Upon receiving the DHCP request,the DHCP server can use the consistent hash algorithm to randomly selector redirect the TFTP client to a TFTP server. This random selection canmake sure the workload balance and will remove any potential bottlenecksfrom any one TFTP server in the cluster.

The method further includes dividing the requested data into severalparts and caching among multiple TFTP servers. For example, a requestedfile that can be downloaded by a TFTP client is divided among aplurality of TFTP servers. Additionally, all cached data is added to aglobal distributed cache, also referred to as a global cache, once therequest rate reaches a certain threshold. For example, upon determiningthat the request rate of a certain data block has reached a pre-definedfirst threshold, a global cache software adds the data block to a globalcache to speed up the transfer rate and reduce disk reads. Each TFTPserver in the cluster can maintain a global cache for the portion of thedivided data that the TFTP server is responsible for. In another exampleembodiment, two or more TFTP servers can each contain multiple copies ofthe data blocks of the first portion of the data file on a plurality ofTFTP servers to enable a high availability for reading blocks in theglobal cache, in the event one of the TFTP server fails unexpectedly. Inone example embodiment, a global cache software can append metadata tothe last data block that can direct the TFTP client to the next datablock, also referred to as the next logical block, on a different TFTPserver. For example, a TFPT client requesting data on a first TFTPserver can reach the end of the cached data (e.g., divided data) forthat file on the first TFPT server. Upon transmitting the last datablock, a global cache software can append metadata to the last blockthat directs the TFTP client to a second TFTP server where the next datablock is cached. Stated another way, the global cache software canrandomly select a second TFTP server, wherein the second TFTP servercontains a second portion of the data file. In another exampleembodiment, a global cache software can utilize a hash algorithm todetermine the location of the next divided data on a next TFTP server.For example, a global cache software can determine the next TFTP serverin the cluster that contains the next data block in the transfer.

The method further includes adjusting the adjusting the global cacheusing a sliding window. For example, as one or more TFTP clients requestcertain data blocks on a first TFTP server, a global cache software willmonitor the read requests. Upon determining that the read requests for aparticular data block have reached above a certain level, the globalcache software can add the data block to the global cache. As the one ormore TFTP clients request a next data block, the request rate for thetail end data blocks will fall below a second threshold level. Upondetermining that the read requests for a tail end data block have fallenbelow a certain level, the global cache software can remove the tail enddata block from the global cache.

Embodiments of the present invention can improve distributed filetransfers with high performance and reliability by checking forrequested data in a global distributed cache before reading the datafrom a disk, thus improving performance of reading from disk andincreasing the throughput and I/O.

Embodiments in accordance with the present invention will now bedescribed in detail with reference to the FIG. FIG. 1 is a functionalblock diagram, generally designated 100, illustrating a distributed filetransfer environment, in an embodiment in accordance with the presentinvention. It should be appreciated that FIG. 1 provides only anillustration of one implementation and does not imply any limitationswith regard to the environments in which different embodiments may beimplemented. Many modifications to the depicted environment may be made.In one example embodiment, distributed file transfer environment 100consists of many TFTP servers with thousands of TFTP clients.

Distributed file transfer environment 100 includes TFTP clients 102,108, 114, 120 TFTP server 130, 144, 158 and other computing devices (notshown), all interconnected over network 128. TFTP client 102 may be aWeb server, or any other electronic device or computing system, capableof processing program instructions and receiving and sending data. Insome embodiments, TFTP client 102 may be a laptop computer, a tabletcomputer, a netbook computer, a personal computer (PC), a desktopcomputer, a personal digital assistant (PDA), a smart phone, or anyprogrammable electronic device capable of communicating over a dataconnection to network 128. In other embodiments, TFTP client 102 mayrepresent server computing systems utilizing multiple computers as aserver system, such as in a distributed computing environment. Ingeneral, TFTP client 102 is representative of any electronic device orcombinations of electronic devices capable of executing machine-readableprogram instructions and communicating with TFTP server 130, 144, and158 via network 128 and with various components and devices (not shown)within distributed file transfer environment 100.

TFTP client 102 includes persistent storage 104. Persistent storage 104may, for example, be a hard disk drive. Alternatively, or in addition toa magnetic hard disk drive, persistent storage 104 may include a solidstate hard drive, a semiconductor storage device, read-only memory(ROM), erasable programmable read-only memory (EPROM), flash memory, orany other computer-readable storage medium that is capable of storingprogram instructions or digital information. TFTP client 102 may includeinternal and external hardware components, as depicted and described infurther detail with respect to FIG. 6.

Software 106 is stored in persistent storage 104, which also includesoperating system software (not shown), as well as software that enablesTFTP client 102 to initiate a file transfer from an TFTP server cluster(e.g., TFTP server 130, 144, and 158), and communicate with othercomputing devices (not shown) of distributed file transfer environment100 over a data connection on network 128. In other example embodiments,software 106 may be components of an operating system software.

Software 106 is a computer program, or sets of computer programs, thatare stored in persistent storage 104. In one example embodiment,software 106 enables TFTP client 102 to download an operating systemimage from the TFTP server cluster (e.g., TFTP server 130, 144, and158), over a data connection to network 128.

TFPT client 108 is also included in distributed file transferenvironment 100. In the present example embodiment, TFPT client 108 isrepresentative of TFTP client 102, including persistent storage 110 thatcontains software 112. Software 112 enables TFTP client 108 to downloadan operating system image from the TFTP server cluster (e.g., TFTPserver 130, 144, and 158), over a data connection to network 128.

TFPT client 114 is also included in distributed file transferenvironment 100. In the present example embodiment, TFPT client 114 isrepresentative of TFTP client 102, including persistent storage 116 thatcontains software 118. Software 118 enables TFTP client 114 to downloadan operating system image from the TFTP server cluster (e.g., TFTPserver 130, 144, and 158), over a data connection to network 128.

TFPT client 120 is also included in distributed file transferenvironment 100. In the present example embodiment, TFPT client 120 isrepresentative of TFTP client 102, including persistent storage 122 thatcontains software 124. Software 124 enables TFTP client 120 to downloadan operating system image from the TFTP server cluster (e.g., TFTPserver 130, 144, and 158), over a data connection to network 128. Thepresent example embodiment assumes there are many TFTP clients (e.g., athousand or more), in distributed file transfer environment 100.

In FIG. 1, network 128 is shown as the interconnecting fabric betweenTFTP client 102, 108, 114, and 120, and TFTP server 130, 144, and 158,and with various components and devices (not shown) within distributedfile transfer environment 100. In practice, the connection may be anyviable data transport network, such as, for example, a LAN or WAN.Network 128 can be for example, a local area network (LAN), a wide areanetwork (WAN) such as the Internet, or a combination of the two, andinclude wired, wireless, or fiber optic connections. In general, network128 can be any combination of connections and protocols that willsupport communications between TFTP client 102, 108, 114, and 120, andTFTP server 130, 144, and 158, and with various components and devices(not shown) within distributed file transfer environment 100.

TFTP server 130 is included in distributed file transfer environment100. TFTP server 130 includes random access memory (RAM) 132, centralprocessing unit (CPU) 134, and persistent storage 136. TFTP server 130may be a Web server, or any other electronic device or computing system,capable of processing program instructions and receiving and sendingdata. In some embodiments, TFTP server 130 may be a laptop computer, atablet computer, a netbook computer, a personal computer (PC), a desktopcomputer, a personal digital assistant (PDA), a smart phone, or anyprogrammable electronic device capable of communicating over a dataconnection to network 128. In other embodiments, TFTP server 130 mayrepresent server computing systems utilizing multiple computers as aserver system, such as in a distributed computing environment. Ingeneral, TFTP server 130 is representative of any electronic devices orcombinations of electronic devices capable of executing machine-readableprogram instructions and communicating with TFTP client 102 via network128 and with various components and devices (not shown) withindistributed file transfer environment 100.

TFTP server 130 includes persistent storage 136. Persistent storage 36may, for example, be a hard disk drive. Alternatively, or in addition toa magnetic hard disk drive, persistent storage 136 may include a solidstate hard drive, a semiconductor storage device, read-only memory(ROM), erasable programmable read-only memory (EPROM), flash memory, orany other computer-readable storage medium that is capable of storingprogram instructions or digital information. Global cache software 138and data 142 are stored in persistent storage 136. Persistent storage136 also includes operating system software (not shown), as well assoftware that enables TFTP server 130 to detect and establish aconnection to TFTP client 102, 108, 114, and 120, server 144, and 158and communicate with other computing devices (not shown) of distributedfile transfer environment 100 over a data connection on network 128.

Global cache software 138 is a computer program, or set of computerprograms, such as application program interface (APIs), that is storedin persistent storage 136. Global cache software 138 is used during afile transfers to place data blocks in a global cache when read requestsfor the data blocks reach a certain threshold (e.g., the firstthreshold). For example, as TFTP client 102, 108, 114, and 120 arebooting up at the same time, global cache software 138 detects therequest rate for a certain data block of data 142 exceeding a certainthreshold. Global cache software 138 then adds the requested data blockto the global cache to reduce the number of reads from persistentstorage 136. Metadata is appended to the last block directing TFTPclient 102, 108, 114, and 120 to a next data block on TFTP server 130,144, and/or 158.

Data 142 is also contained in persistent storage 136. In the exampleembodiment of FIG. 1, data 142 is a part of a larger operating systemimage that is divided up among the TFTP server cluster (e.g., TFTPserver 130, 144, and 158). For example TFTP server 130 can contain aportion of the operating system image in persistent storage 136, TFTPserver 144 can contain another portion of the operating system image inpersistent storage 150, and TFTP server 158 can contain the finalportion of the operating system image in persistent storage 164.

TFPT server 144 is also included in distributed file transferenvironment 100. In the present example embodiment, TFPT server 144 isrepresentative of TFTP server 130, including RAM 146, CPU 148, andpersistent storage 150. Persistent storage 150 contains a global cachesoftware 152 and data 156. Persistent storage 150 also includesoperating system software (not shown), as well as software that enablesTFTP server 144 to detect and establish a connection to TFTP client 102,108, 114, and 120, server 130, and 158 and communicate with othercomputing devices (not shown) of distributed file transfer environment100 over a data connection on network 128.

Global cache software 152 is a computer program, or set of computerprograms, such as application program interface (APIs), that is storedin persistent storage 150. Global cache software 152 is used during filetransfers to place data blocks in a global cache when read requests forthe data blocks reach a certain threshold, such as the first threshold.For example, upon reaching the end of a data block on a previous TFTPserver (e.g., TFTP server 130), TFTP client 102 is directed to the nextdata block stored on TFTP server 144. For example, global cache software138 on TFTP server 130 can apply a hash algorithm to determine the nextTFTP server in the transfer. Global cache software 138 can then addmetadata to the last data block that instructs TFTP client 102 to TFTPserver 144.

Data 156 is also contained in persistent storage 150. Continuing withthe previous example, data 156 is a portion of the divided data storedamong TFTP server 130, 144, and 158.

TFPT server 158 is also included in distributed file transferenvironment 100. In the present example embodiment, TFPT server 158 isrepresentative of TFTP server 130 and 144, including RAM 160, CPU 162,and persistent storage 164. Persistent storage 164 contains a globalcache software 166 and data 170. Persistent storage 164 also includesoperating system software (not shown), as well as software that enablesTFTP server 158 to detect and establish a connection to TFTP client 102,108, 114, and 120, server 130, and 144 and communicate with othercomputing devices (not shown) of distributed file transfer environment100 over a data connection on network 128.

Global cache software 166 is a computer program, or set of computerprograms, such as application program interface (APIs), that is storedin persistent storage 164. Global cache software 166 is used during filetransfers to place data blocks in a global cache when read requests forthe data blocks reach a certain threshold, such as the first threshold.For example, upon reaching the end of a data block on a previous TFTPserver (e.g., TFTP server 144), TFTP client 102 is directed to the nextdata block stored on TFTP server 158. For example, global cache software152 on TFTP server 144 can apply a hash algorithm to determine the nextTFTP server in the transfer. Global cache software 152 can then addmetadata to the last data block that instructs TFTP client 102 to TFTPserver 158.

Data 170 is also contained in persistent storage 164. Continuing withthe previous example, data 170 is a portion of the divided data storedamong TFTP server 130, 144, and 158. In other example embodiments, TFTPserver 130, 144, and 158 can contain the entire data, such as anoperating system image. A global cache software can then identifyportions of the operating system image on TFTP server 130, 144, and 158to be downloaded by one or more TFTP clients. In other exampleembodiments, global cache software on TFTP server 130, 144, and 158 candynamically adjust the identified portions operating system image. Forexample, global cache software 152 can determine the next server in thecluster is currently experiencing high downloads and can adjust thedivided portion of the operating system image to compensate. Upondetecting that the download rate has dropped below a certain threshold(e.g., the second threshold), global cache software 152 can then directthe client to the next server.

FIG. 2 is a flowchart, generally designated 200, depicting operationalsteps of a global cache software, on a TFTP server cluster within thedistributed file transfer environment of FIG. 1, for inserting a headdata block in a global cache, in an embodiment in accordance with thepresent invention. In one example embodiment, a plurality of TFTPclients (e.g., TFTP client 102, 108, 114, and 120), begin requestingdata blocks from one or more TFTP servers (e.g., TFTP server 130, 144,and 158), in a server cluster within distributed file transferenvironment 100. For example, TFTP client 102, 108, 114, and 120 requestone or more data blocks of an operating system image stored among thecluster.

In decision step 202, global cache software 138 determines if there is adata block in the global cache list. For example, when the request rateof a particular data block reaches a certain threshold such as the firstthreshold, global cache software 138 will add the data block to theglobal cache to speed up, adapt, or optimize, the desired transfer rateand reduce reads from one or more hard drives. In one exampleembodiment, global cache software 138 can check the global cache uponreceiving a request for a data block. In other example embodiments,global cache software 138 can check the global cache at random orconfigured intervals.

If global cache software 138 determines if there is no data block in theglobal cache list (“No” branch, decision 202), global cache software 138monitors all incoming requests for data blocks as depicted in step 204.For example, upon determining that there are no data blocks in theglobal cache, global cache software 138 can continue monitoring theincoming requests for data blocks of the portion of the dividedoperating system image (e.g., data 142), stored in persistent storage136.

In decision step 206, global cache software 138 determines if therequest rate of a data block has reached a certain threshold. Forexample, global cache software 138 determines that the request rate of acertain data block has reached a defined threshold, such as the firstthreshold set by an administrator, or by global cache software 138. Thedefined threshold is reached when a plurality of TFTP clients requestthe data block in a short period of time. In one example embodiment, anadministrator can set the first threshold level using a user interfaceon TFTP server 130. In another example embodiment, the request rate ofthe first threshold can be dynamically set and/or adjusted by globalcache software 138 based on the current throughput of: (i) the networkbandwidth, (ii) a current network throughput, and (iii) the current harddisk throughput.

If global cache software 138 determines that the request rate of a datablock has not reached a certain threshold (“No” branch, decision 206),global cache software 138 continues to monitor all incoming requests fordata blocks as depicted in step 204. For example, global cache software138 determines that the request rate for a given data block is below thepreviously set first threshold level. Upon determining that the requestrate is not above the required first threshold level to add the datablock to the global cache, global cache software 138 continues tomonitor the incoming requests for data blocks. In another exampleembodiment, global cache software 138 can add requested data blocks tothe global cache when the request rate for a certain data block is low.

If global cache software 138 determines that the request rate of a datablock has reached a certain threshold (“Yes” branch, decision 206),global cache software 138 then adds the requested data block into theglobal cache as depicted in step 208. For example, global cache software138 receives multiple requests for a data block of data 142. Upondetermining that the request rate to the data block exceeds the firstthreshold, global cache software 138 adds the data block to the globalcache then repeats decision 202 as depicted in FIG. 2.

If global cache software 138 determines if there is a data block in theglobal cache list (“Yes” branch, decision 202), global cache software138 monitors all incoming requests for the head data block as depictedin step 210. In other words, in step 210, global cache software 138monitors incoming file requests to determine the first data block of therequested file that is not included in the global cache. For example,global cache software 138 determines that a plurality of data blocks(e.g., data block 301, 302, 303, 304, 308, 309, and 310), are alreadyplaced in global cache 300 as depicted in global cache 300 of FIG. 3A.The “head data block” of the file would be the first data block notincluded in global cache 300 (for example, data block 305, discussedbelow.

In decision step 212, global cache software 138 determines if therequest rate of the head data block has reached a certain threshold. Forexample, global cache software 138 determines if the request rate forthe head data block, also referred to as the next data block, in thefile transfer has reached a certain request rate threshold, (e.g., thefirst threshold), wherein the first request rate threshold is aconfigurable limit that defines when data blocks are to be added to theglobal cache.

If global cache software 138 determines that the request rate of thehead data block has not reached a certain threshold (“No” branch,decision 212), global cache software 138 continues to monitor allincoming requests for the head data block as depicted in step 210. Forexample, global cache software 138 determines that the request rate forthe head data block is below the previously set first threshold level.Upon determining that the request rate is not above the required firstthreshold level to add the head data block to the global cache, globalcache software 138 continues to monitor the incoming requests for thedata block. In another example embodiment, global cache software 138 canadd one or more requested head data blocks to the global cache when therequest rate for the one or more requested head data blocks is low.

If global cache software 138 determines that the request rate of thehead data block has reached a certain threshold (“Yes” branch, decision212), global cache software 138 then adds the requested head data blockinto the global cache as depicted in step 214. For example, global cachesoftware 138 receives multiple requests for one or more head data blocksof data 142. Upon determining that the request rate of the one or morehead data blocks exceed the first threshold level, global cache software138 then adds the head data blocks (e.g., head data block 305 and 312 asdepicted in FIG. 3B) to the global cache then repeats decision 202 asdepicted in FIG. 2.

In a deployment of large scale cluster, such as distributed filetransfer environment 100, the cluster nodes (e.g., TFTP client 102, 108,114, and 120), will request access to the same file. Over a certain timeperiod, the offset of reading the file by most of the nodes in thecluster will be in a certain consecutive interval, and as timeprogresses, the read offset will move forward. Some embodiments of thepresent invention include the following features: (i) the global cacheonly includes the consecutive blocks, and the number of consecutiveblocks can be set to N, if N=1, the algorithm will be simplified as LRU(Least Recently Used); (ii) the global cache can include multipleconsecutive intervals (e.g., data block 301, 302, 303, 304, and 308,309, 310 in FIG. 3A), the number of consecutive intervals can be set toM, where M depends on N and the global maximum cache SIZE; (iii) amove-in rule where the global cache software counts the access frequencyof the data block (e.g., X1.start˜X2.start), and if the access frequencyof the data block reaches the first threshold level, the data blockswill be moved into global cache and the next value, also referred to asthe next possible data block, being counted will be set toX2.start˜X3.start (e.g., data block 305 and 312 moved into global cache300 in FIG. 3B); and (iv) a move-out rule where the access frequency ofthe first data block moved into the global cache, that is part of aconsecutive interval, drops below the second threshold, the first datablock will be moved out the global cache.

In another example embodiment, global cache software 138 can use themove-in rule to predict the next data block as shown in the exampleembodiment of FIG. 3A and FIG. 3B. For example, as the request rate ofthe sliding window (e.g., data block 301, 302, 303, 304, and 308, 309,310 as depicted in FIG. 3A), changes, global cache software 138 canpredict when requests for the next data block will be likely to exceedthe defined first request rate threshold. For example, as the requestrate for data block 304 and 310 reach a defined threshold, such as thefirst threshold level, and are added into global cache 300, global cachesoftware 138 can begin monitoring data block 305 and 312. Upondetermining that the request rate of data blocks 305 and 312 havereached the first threshold level, global cache software 138 can predictwhen data block 305 and 312 will need to be added to global cache 300.

FIG. 4 is a flowchart, generally designated 400, depicting operationalsteps of a global cache software, on a TFTP server cluster within thedistributed file transfer environment of FIG. 1, for removing tail enddata block from a global cache, in an embodiment in accordance with thepresent invention. Continuing the example embodiment of FIG. 2, whereglobal cache software 138 uses the move in rule to add multipleconsecutive data block 301, 302, 303, 304, 305, and 308, 309, 310, 312as depicted in FIGS. 3A and 3B, global cache software 138 can then usethe move out rule to drop, or remove, data blocks that fall below acertain threshold, such as the second threshold level.

In step 402, global cache software 138 monitors all incoming requestsfor the end block in the global cache. For example, global cachesoftware 138 monitors data block 301 and 308. In the example embodimentof FIG. 5A, data block 301 and 308 are the first data blocks added tothe multiple consecutive intervals of data block 301, 302, 303, 304,305, and 308, 309, 310, 312 by global cache software 138. In otherexample embodiments, the number of multiple consecutive intervals can beconfigured by an administrator, or dynamically by global cache software138. For example, a network administrator can set a parameter on TFTPserver 130 that global cache software 138 can use to allow a certainnumber of multiple consecutive intervals of data blocks to be placed inglobal cache 300.

In decision step 404, global cache software 138 checks if the requestrate of the end block is below a certain threshold. For example, globalcache software determines if the request rate for data block 301 and/or308 has fallen below a configured threshold, such as the secondthreshold level. If global cache software 138 determines that therequest rate of the end block is not below a certain threshold (“No”branch, decision 404), global cache software 138 continues to monitorall incoming requests for the end blocks in the global cache as depictedin step 402. If global cache software 138 determines that the requestrate of the end block is below a certain threshold (“Yes” branch,decision 404), global cache software 138 deletes the end block from theglobal cache as depicted in step 406. For example, referring to FIG. 5A,global cache software 138 determines that the request rate for datablock 301 and 308 is below the second threshold level and removes datablock 301 and 308 from global cache 300 as depicted in FIG. 5B.

Embodiments of the present invention provide an advantage over thetraditional master-client configurations and the traditionalmaster-client configurations using multiple TFTP servers by solving thebuffer bottleneck problem of a single HOST (i.e., TFTP server), byimproving the size of the read buffer (e.g., by implementing globalcache 300) and enhancing the performance of the valid buffer. Forexample, embodiments of the present invention can do this by onlyplacing data blocks in global cache 300 that are in high demand, andremoving data blocks that are low in demand. Global cache 300 also fixesbuffer volume problems seen in the traditional master-clientconfigurations when many (e.g., thousands), of TFTP clients request thesame file. For example, as more TFTP clients execute a boot sequence andrequest a file from the master TFTP server, the buffer volume of themaster TFTP server becomes a bottleneck. By utilizing a TFTP servercluster (e.g., TFTP server 130, 144, and 158), the demand on buffers canbe divided among the plurality of the TFTP servers.

Embodiments of the present invention provide an advantage utilizing aslide-in and slide-out rule to create a sliding window function thatimproves the buffer hit rate of the global cache. The buffer hit rate intraditional master-client configurations does not allow the file to becompletely hit when file size is greater than the valid buffer of thesingle HOST (i.e., TFTP server). Embodiments of the present inventionimprove the whole buffer function by allowing a file to be completelybuffered across the entire cluster, which also improves the hit rate. Tocompare with the traditional methods previously described, if the filesize is greater than the valid buffer of the host (i.e., TFTP server),and the file size is greater than the global buffer, the slide windowfunction can be effective in a large cluster deployment. For example,most of the nodes (TFTP clients), will access the same file areas in acertain interval. The reading rate threshold (e.g., the firstthreshold), for the head-most block in the global cache can beconfigured. A small reading rate threshold can greatly enhance theglobal cache hit rate. As a result, the global buffer will grow with thegrowth of the TFTP server, and the sequential buffer file will growaccording to the sequential file rule. According to embodiments of thepresent invention, if the first threshold level is low enough and allnodes in the environment access the host at the same time, then allnodes except the first node—which needs to read from disk—will read fromthe global cache. For example, if the first threshold level is 10percent, then the remaining 90 percent of clients will read from theglobal buffer. In some embodiments, the best scenario is a global cachehit rate of 100%. For example, in a best case scenario the average timerequired for 1024 nodes to transfer data can be seen below:

$\frac{\left( {16\mspace{20mu} G*1024} \right)}{1\mspace{20mu} G} = {4.5\mspace{14mu}{hours}}$

In this example, 100 percent of the requested data is read from theglobal cache with an access rate of 16 Gigabytes per second for 1024nodes and an average access rate of 1 Gigabyte per second for each node.Therefore, the time required for 1024 nodes would be 4.5 hours.

Embodiments of the present invention can be applied to any file transferprotocol (FTP) environment comprised of a FTP server cluster, whereineach FTP server in the FTP server cluster is fully symmetric of oneanother.

FIG. 6 depicts a block diagram, generally designated 600, of componentsof the TFTP server executing the global cache software, in an embodimentin accordance with the present invention. It should be appreciated thatFIG. 6 provides only an illustration of one implementation and does notimply any limitations with regard to the environments in which differentembodiments may be implemented. Many modifications to the depictedenvironment may be made.

TFTP server 130 includes communications fabric 602, which providescommunications between computer processor(s) 604, memory 606, persistentstorage 608, communications unit 610, and input/output (I/O)interface(s) 612. Communications fabric 602 can be implemented with anyarchitecture designed for passing data and/or control informationbetween processors (such as microprocessors, communications and networkprocessors, etc.), system memory, peripheral devices, and any otherhardware components within a system. For example, communications fabric602 can be implemented with one or more buses.

Memory 606 and persistent storage 608 are computer readable storagemedia. In this embodiment, memory 606 includes random access memory(RAM) 614 and cache memory 616. In general, memory 606 can include anysuitable volatile or non-volatile computer readable storage media.

Global cache software 622 and data 624 are stored in persistent storage608 for execution and/or access by one or more of the respectivecomputer processors 604 via one or more memories of memory 606. In thisembodiment, persistent storage 608 includes a magnetic hard disk drive.Alternatively, or in addition to a magnetic hard disk drive, persistentstorage 608 can include a solid state hard drive, a semiconductorstorage device, read-only memory (ROM), erasable programmable read-onlymemory (EPROM), flash memory, or any other computer readable storagemedia that is capable of storing program instructions or digitalinformation.

The media used by persistent storage 608 may also be removable. Forexample, a removable hard drive may be used for persistent storage 608.Other examples include optical and magnetic disks, thumb drives, andsmart cards that are inserted into a drive for transfer onto anothercomputer readable storage medium that is also part of persistent storage608.

Communications unit 610, in these examples, provides for communicationswith other data processing systems or devices, including resources ofnetwork 128 and TFTP client 102, 108, 114 and 120, and TFTP server 144,and 158. In these examples, communications unit 610 includes one or morenetwork interface cards. Communications unit 610 may providecommunications through the use of either or both physical and wirelesscommunications links. Global cache software 622 and data 624 may bedownloaded to persistent storage 608 through communications unit 610.

I/O interface(s) 612 allows for input and output of data with otherdevices that may be connected to TFTP server 130. For example, I/Ointerface 612 may provide a connection to external devices 618 such as akeyboard, keypad, a touch screen, and/or some other suitable inputdevice. External devices 618 can also include portable computer readablestorage media such as, for example, thumb drives, portable optical ormagnetic disks, and memory cards. Software and data used to practiceembodiments of the present invention, e.g., global cache software 622and data 624, can be stored on such portable computer readable storagemedia and can be loaded onto persistent storage 608 via I/O interface(s)612. I/O interface(s) 612 also connect to a display 620.

Display 620 provides a mechanism to display data to a user and may be,for example, a computer monitor.

The programs described herein are identified based upon the applicationfor which they are implemented in a specific embodiment of theinvention. However, it should be appreciated that any particular programnomenclature herein is used merely for convenience, and thus theinvention should not be limited to use solely in any specificapplication identified and/or implied by such nomenclature.

The present invention may be a system, a method, and/or a computerprogram product at any possible technical detail level of integration.The computer program product may include a computer readable storagemedium (or media) having computer readable program instructions thereonfor causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, configuration data for integrated circuitry, oreither source code or object code written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Smalltalk, C++, or the like, and procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The computer readable program instructions may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider). In some embodiments, electronic circuitry including,for example, programmable logic circuitry, field-programmable gatearrays (FPGA), or programmable logic arrays (PLA) may execute thecomputer readable program instructions by utilizing state information ofthe computer readable program instructions to personalize the electroniccircuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in the Figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Definitions

“Present invention” does not create an absolute indication and/orimplication that the described subject matter is covered by the initialset of claims, as filed, by any as-amended set of claims drafted duringprosecution, and/or by the final set of claims allowed through patentprosecution and included in the issued patent. The term “presentinvention” is used to assist in indicating a portion or multipleportions of the disclosure that might possibly include an advancement ormultiple advancements over the state of the art. This understanding ofthe term “present invention” and the indications and/or implicationsthereof are tentative and provisional and are subject to change duringthe course of patent prosecution as relevant information is developedand as the claims may be amended.

“Embodiment,” see the definition for “present invention.”

“And/or” is the inclusive disjunction, also known as the logicaldisjunction and commonly known as the “inclusive or.” For example, thephrase “A, B, and/or C,” means that at least one of A or B or C is true;and “A, B, and/or C” is only false if each of A and B and C is false.

A “set of” items means there exists one or more items; there must existat least one item, but there can also be two, three, or more items. A“subset of” items means there exists one or more items within a groupingof items that contain a common characteristic.

A “plurality of” items means there exists more than one item; there mustexist at least two items, but there can also be three, four, or moreitems.

“Includes” and any variants (e.g., including, include, etc.) means,unless explicitly noted otherwise, “includes, but is not necessarilylimited to.”

What is claimed is:
 1. A computer-implemented method comprising:creating, by one or more processors on a first Trivial File TransferProtocol (TFTP) server, a global cache, wherein the global cache is usedto store up to a first portion of a data file; storing, by one or moreprocessors on the first TFTP server, in the global cache, one or morecontinuous data blocks that have exceeded a defined first request ratethreshold, wherein the one or more continuous data blocks make up asubset of the data blocks of the first portion of the data file;predicting, by one or more processors on the first TFTP server, a nextdata block in the data file to be stored in the global cache; inresponse to predicting the next data block, storing, by one or moreprocessors on the first TFTP server, the next data block in the globalcache; selecting, by one or more processors on the first TFTP server, asecond TFTP server, wherein the second TFTP server contains a secondportion of the data file; and adding, by one or more processors on thefirst TFTP server, metadata to a last data block of the first portion ofthe data file, wherein the metadata identifies the second TFTP server.2. The computer-implemented method of claim 1, wherein the data file isdivided into a plurality of portions, including the first portion, andwherein the plurality of portions are stored among a plurality of TFTPservers.
 3. The computer-implemented method of claim 1, wherein storing,in the global cache, the one or more continuous data blocks that haveexceeded the defined first request rate threshold comprises: monitoring,by one or more processors on the first TFTP server, a request rate for aparticular data block; determining, by one or more processors on thefirst TFTP server, if the request rate for the particular data blockexceeds the defined first request rate threshold, wherein the definedfirst request rate threshold is a configurable limit that defines whendata blocks are to be added to the global cache, and wherein the definedfirst request rate is adapted to optimize a transfer rate and reducereads from one or more hard drives; and adding, by one or moreprocessors on the first TFTP server, the particular data block to theglobal cache based on the determining.
 4. The computer-implementedmethod of claim 1, further comprising: monitoring, by one or moreprocessors on the first TFTP server, the one or more continuous datablocks in the global cache to determine if the request rate for an enddata block of the one or more continuous data blocks has fallen below adefined second request rate threshold, wherein the defined secondrequest rate threshold is a configurable limit that defines when the oneor more continuous data blocks in the global cache can be removed fromthe global cache; and in response to determining that the end data blockof the one or more continuous data blocks has fallen below the definedsecond request rate threshold, removing, by one or more processors onthe first TFTP server, the end data block from the one or morecontinuous data blocks stored in the global cache.
 5. Thecomputer-implemented method of claim 1, further comprising storing, byone or more processors on the first TFTP server, multiple copies of thedata blocks of the first portion of the data file on a plurality of TFTPservers to enable a high availability for reading one or more blocks inthe global cache.
 6. A computer program product comprising: one or morecomputer readable storage media and program instructions stored on theone or more computer readable storage media, the stored programinstructions comprising: program instructions to create, by a firstTrivial File Transfer Protocol (TFTP) server, a global cache, whereinthe global cache is used to store up to a first portion of a data file;program instructions to store, by the first TFTP server, in the globalcache, one or more continuous data blocks that have exceeded a definedfirst request rate threshold, wherein the one or more continuous datablocks make up a subset of the data blocks of the first portion of thedata file; program instructions to predict, by the first TFTP server, anext data block in the data file to be stored in the global cache;program instructions to, in response to predicting the next data block,store, by the first TFTP server, the next data block in the globalcache; program instructions to select, by the first TFTP server, asecond TFTP server, wherein the second TFTP server contains a secondportion of the data file; and program instructions to add, by the firstTFTP server, metadata to a last data block of the first portion of thedata file, wherein the metadata identifies the second TFTP server. 7.The computer program product of claim 6, wherein the data file isdivided into a plurality of portions, including the first portion, andwherein the plurality of portions are stored among a plurality of TFTPservers.
 8. The computer program product of claim 6, wherein the programinstructions to store, in the global cache, the one or more continuousdata blocks that have exceeded the defined first request rate thresholdcomprise: program instructions to monitor, by the first TFTP server, arequest rate for a particular data block; program instructions todetermine, by the first TFTP server, if the request rate for theparticular data block exceeds the defined first request rate threshold,wherein the defined first request rate threshold is a configurable limitthat defines when data blocks are to be added to the global cache, andwherein the defined first request rate is adapted to optimize a transferrate and reduce reads from one or more hard drives; and programinstructions to add, by the first TFTP server, the particular data blockto the global cache based on the determining.
 9. The computer programproduct of claim 6, the stored program instructions further comprising:program instructions to monitor, by the first TFTP server, the one ormore continuous data blocks in the global cache to determine if therequest rate for an end data block of the one or more continuous datablocks has fallen below a defined second request rate threshold, whereinthe defined second request rate threshold is a configurable limit thatdefines when the one or more continuous data blocks in the global cachecan be removed from the global cache; and program instructions to, inresponse to determining that the end data block of the one or morecontinuous data blocks has fallen below the defined second request ratethreshold, remove, by the first TFTP server, the end data block from theone or more continuous data blocks stored in the global cache.
 10. Thecomputer program product of claim 6, the stored program instructionsfurther comprising program instructions to store, by the first TFTPserver, multiple copies of the data blocks of the first portion of thedata file on a plurality of TFTP servers to enable a high availabilityfor reading one or more blocks in the global cache.
 11. A computersystem comprising: one or more computer processors; one or more computerreadable storage media; program instructions stored on the computerreadable storage media for execution by at least one of the one or moreprocessors, the stored program instructions comprising: programinstructions to create, by a first Trivial File Transfer Protocol (TFTP)server, a global cache, wherein the global cache is used to store up toa first portion of a data file; program instructions to store, by thefirst TFTP server, in the global cache, one or more continuous datablocks that have exceeded a defined first request rate threshold,wherein the one or more continuous data blocks make up a subset of thedata blocks of the first portion of the data file; program instructionsto predict, by the first TFTP server, a next data block in the data fileto be stored in the global cache; program instructions to, in responseto predicting the next data block, store, by the first TFTP server, thenext data block in the global cache; program instructions to select, bythe first TFTP server, a second TFTP server, wherein the second TFTPserver contains a second portion of the data file; and programinstructions to add, by the first TFTP server, metadata to a last datablock of the first portion of the data file, wherein the metadataidentifies the second TFTP server.
 12. The computer system of claim 11,wherein the data file is divided into a plurality of portions, includingthe first portion, and wherein the plurality of portions are storedamong a plurality of TFTP servers.
 13. The computer system of claim 11,wherein the program instructions to store, in the global cache, the oneor more continuous data blocks that have exceeded the defined firstrequest rate threshold comprise: program instructions to monitor, by thefirst TFTP server, a request rate for a particular data block; programinstructions to determine, by the first TFTP server, if the request ratefor the particular data block exceeds the defined first request ratethreshold, wherein the defined first request rate threshold is aconfigurable limit that defines when data blocks are to be added to theglobal cache, and wherein the defined first request rate is adapted tooptimize a transfer rate and reduce reads from one or more hard drives;and program instructions to add, by the first TFTP server, theparticular data block to the global cache based on the determining. 14.The computer system of claim 11, the stored program instructions furthercomprising: program instructions to monitor, by the first TFTP server,the one or more continuous data blocks in the global cache to determineif the request rate for an end data block of the one or more continuousdata blocks has fallen below a defined second request rate threshold,wherein the defined second request rate threshold is a configurablelimit that defines when the one or more continuous data blocks in theglobal cache can be removed from the global cache; and programinstructions to, in response to determining that the end data block ofthe one or more continuous data blocks has fallen below the definedsecond request rate threshold, remove, by the first TFTP server, the enddata block from the one or more continuous data blocks stored in theglobal cache.
 15. The computer system of claim 11, the stored programinstructions further comprising program instructions to store, by thefirst TFTP server, multiple copies of the data blocks of the firstportion of the data file on a plurality of TFTP servers to enable a highavailability for reading one or more blocks in the global cache.